Once the Cold War ended it didn't make much sense for neoconservatives and small-government conservatives to remain in a coalition. But breakups take time, and post-9/11 politics briefly created the illusion that Bill Kristol and George Will belong in the same political party. I am here to tell you that they do not, even if many people who identify as small-government conservatives still don't realize it.

There are kind, intellectually honest neoconservatives who genuinely believe that their hawkish, imperial approach to foreign policy would bring about a better world. Their notion of the good is still incompatible with small-government conservatism and libertarianism. And the darkest strains in neoconservatism—the zealous defenses of torturing prisoners, for example—are incompatible with the professed beliefs of a lot of social and religious conservatives, too. How could the GOP possibly serve the agendas of all these factions?

If neoconservatives got their way, as they did during George W. Bush's first term, the United States would spend more on its military and wage war in more countries. Neoconservatives still believe the Iraq War was a good idea. They'd have preferred to keep our troops in Afghanistan longer. They urged greater American involvement in Egypt and Libya. They wanted President Obama to intervene in Syria.

As they urge actions that would require spending tens of billions of additional dollars in the Middle East and North Africa, they also insist that NATO grant security guarantees to countries like Georgia, as if the sanctity of its borders is worth risking nuclear war. And having urged a geopolitical strategy that stretches America thin across much of the rest of the world, they criticize the Obama Administration for not doing enough to "pivot toward Asia" in the Pacific.

Many small-government conservatives may be morally comfortable with interventionism. What they must realize is that neoconservatism's particular agenda would require dramatic tax increases, or significant borrowing, to carry out; that neoconservative strategists have shown an utter inability to produce competent analysis of how the interventions that they favor will unfold; and that the costs are often borne by the young Americans who are killed or maimed in lost wars.

If neoconservative publications favor expensive wars but advocate against liberal domestic spending, is that a wash? Hardly.

What are the monetary costs of the neoconservative agenda? Rank-and-file Republicans often underestimate them. If neoconservative publications favor expensive wars but advocate against liberal domestic spending, is that a wash? Hardly. Once everything is factored in, the Iraq War alone may cost America $6 trillion. $6 trillion!

That's roughly $20,000 for every living American.

Small-government conservatives are also inclined to forget that war is the health of the state. Every significant war that America undertakes significantly increases the power of the federal government, even outside the realm of war, exacting heavy costs in liberty. War can still be necessary. I'd put the Civil War and World War II in that category. Other times, war brings more costs than benefits. But virtually all wars concentrate more power in the state and reduce domestic freedom. America's war and small-government factions are at cross-purposes.

When one wins the other loses.

Neoconservatives aren't alone in touting imprudent foreign interventions and allying with the national security state even when it is infringing upon the rights of innocent people. Though Hillary Clinton comes from a different intellectual tradition, for example, she has supported numerous wars of choice and illiberal policies. And the aughts featured a host of Republicans who weren't exactly neoconservatives, but backed the invasion of Iraq, torture, and indefinite detention.

But a hyper-interventionist foreign policy is the thing that neoconservatives care about most. It's the priority that they'll negotiate for, not a soft preference they'll negotiate away. That's why it makes sense for small-government conservatives to do all they can to diminish neoconservative influence within the GOP, just as it makes sense for neoconservatives to do all they can to diminish libertarian influence.

This may become much more clear to Republicans in the next presidential election. The odds of any given matchup coming to fruition are long. But if Election 2016 turns out to pit Rand Paul against Hillary Clinton, lots of neoconservatives will vote for the Democrat, as they should, given their ideological notions of what's right for the world. If that happens, it will be fascinating to see what The Weekly Standard publishes in the back of the book circa 2017.

Conor Friedersdorf is a staff writer at The Atlantic, where he focuses on politics and national affairs. He lives in Venice, California, and is the founding editor of The Best of Journalism, a newsletter devoted to exceptional nonfiction.